Docosahexanoic acid signals through the Nrf2–Nqo1 pathway to maintain redox balance and promote neurite outgrowth

Evidence suggests that n-3 polyunsaturated fatty acids may act as activators of the Nrf2 antioxidant pathway. The antioxidant response, in turn, promotes neuronal differentiation and neurite outgrowth. Nrf2 has recently been suggested to be a cell intrinsic mediator of docosohexanoic acid (DHA) signaling. In the current study, we assessed whether DHA-mediated axodendritic development was dependent on activation of the Nrf2 pathway and whether Nrf2 protected from agrochemical-induced neuritic retraction. Expression profiling of the DHA-enriched Fat-1 mouse brain relative to wild type showed a significant enrichment of genes associated with neuronal development and neuronal projection and genes associated with the Nrf2-transcriptional pathway. Moreover, we found that primary cortical neurons treated with DHA showed a dose-dependent increase in Nrf2 transcriptional activity and Nrf2-target gene expression. DHA-mediated activation of Nrf2 promoted neurite outgrowth and inhibited oxidative stress-induced neuritic retraction evoked by exposure to agrochemicals. Finally, we provide evidence that this effect is largely dependent on induction of the Nrf2-target gene NAD(P)H: (quinone acceptor) oxidoreductase 1 (NQO1), and that silencing of either Nrf2 or Nqo1 blocks the effects of DHA on the axodendritic compartment. Collectively, these data support a role for the Nrf2-NQO1 pathway in DHA-mediated axodendritic development and protection from agrochemical exposure.